Mountain Flora of Mexico-Guatemala. 303 
there are indications of prehistoric agriculture and human occupation, so that 
the entire vegetation has been altered by fire used to clear the land of the 
continuous forest growth. — Finally, there is the distinct preponderating element 
which furnishes the prominent features of the whole flora. Setting aside those 
plants characteristic of a dry climate, we find evidence of an enormous de- 
velopment in certain groups of plants which flourish only where there is con- 
siderable humidity. These are the plants that inhabit the eastern slopes and 
ravines, and constitute what we should call the special flora of this province in 
contra-distinction to the southward extensions of north-Mexican flora. Cook 
among other interesting observations states that in Guatemala after the fire- 
swept areas have been cultivated and then abandoned to grass land, the process 
of reforestation may betraced through a succession of temporary types, such 
as pines, oaks, and other tropic trees, such as Acrocomia, Cecropia and Attalea'). 
Yet here northern and southern types meet and commingle in a most remarkable 
manner; and the endemic element is specific, rather than generic. The diversified 
oak-forests laden with epiphytic orchids, bromeliads and other plants equally 
characteristic of the vegetation south of the Isthmus of Panama afford the best 
illustration of the correctness of this statement. It is true the oak type is not 
peculiarly characteristic of a moist climate, but it is essentially northern, and 
although, it has reached the Andes of South America, its development there 
is quite insignificant. On the other hand, the orchids associated with the oaks 
of Mexico belong almost wholly to genera equally, or more strongly represented 
in South America. Thus only nine out of upwards of a hundred genera are 
endemic in our central region; and only fourteen are restricted to the country 
north of the Isthmus of Panama. Further, ten of the fourteen genera are 
monotypes, and the others number very few species; moreover, it is noteworthy 
that nearly as many genera reach eastern, as western South America. 
The flora of Guatemala is essentially of the same composition as that 
of South Mexico, though apparently less rich in specific diversity. Of the eastern 
North American deciduous arboreous types in South Mexico, just alluded to, 
some as T7zha and Ulmus are not known to reach Guatemala, while others 
such as Liguidambar, Morus, Ostrya and Carpinus are present, and the two 
latter have here their southern limit. As might be expected, too, some charac- 
teristic South American types find their northern limit in Guatemala. Note- 
worthy among these are the Vochysiaceae; the genera Vochysia and Trigonia, 
being both represented. 
South American Element. The southern floral province, comprising Nicaragua, 
Costa Rica and Panama exhibits much closer relationship with the South American 
tropic flora, and may be of more recent derivation, but the large number of 
South American types which reach Mexico or Guatemala, and not the West 
Indies, indicate a more remote connection though of course it may not have 
I) Coox, O. F.: Vegetation affected by Agriculture in Central America. Bull. 145. Bureau 
Plant Industry. 
